Ritsuko Akagi is NERV's head scientist and is heavily involved in the repairs and maintenance of Tokyo-3's defenses against the Angels, particularly the Evas.

She is the daughter of Naoko Akagi, the developer of the MAGI supercomputer system which controls Nerv. In many ways, Ritsuko is living in the shadow of her mother, whom she both admires and despises. Naoko was the head scientist working on the Evangelion project before her death, and Ritsuko is continuing the work her mother began with the Evas, as well as continuing the development of the Magi supercomputer system. Flashbacks to a teenaged Ritsuko reveal that she is a natural brunette, just like her mother.

Ritsuko is extremely intelligent, with a strong dedication to her work and a stoic, detached attitude which is frequently contrasted against Misato Katsuragi's hot-headness, especially during Eva combat. Her occasional jibes at Misato are a source of comic relief in the series. She has a great affinity for cats, and Misato chides her at one point for substituting her cats for human affection. She also is a heavy smoker, as evidenced by an ashtray on her desk filled with cigarette butts stained by her lipstick.